Has to be generally the same frame. I would guess it would have a different part number due to some slightly different hole etc, but I bet either would work for either application with minor modifications. (2500 to Power Wagon). IE, I am sure a Cummins, G56, etc would be a bolt in, except for anything obvious (cutting the floorpan for the transmission shifter, winch interferes with intercooler).

Just a pure guess, but the economics wouldn't work for Daimler if they had to do a create new frame.

A few different holes and weldments, but I'm sure the structural members are the same as for a normal Hemi or Cummins 2500 crew 6'4" box. For example, the front track bar frame side mount is different, and that is a weldment.

They are the same for all intents & purposes. But they used to have different part #'s technically speaking. Not sure on the 2017's. Like the others have said, same frame, just some added/different holes for all the Power Wagon goodies. No big mystery here.